Solid state imaging device and method of manufacturing same

ABSTRACT

On the surface of a protecting layer mounted on a solid state imaging devices substrate, transparent gap filler layers and a transparent flattening layer are formed to flatten a surface of overlying protecting layer. On a surface of the transparent flattening layer, color filters of red, blue and yellow are formed. The color filters are made of synthetic photosensitive material. By using the synthetic photosensitive material, the color filters are formed with good shape and precision. All of the color filter show good photo spectrography and uniform characteristics. For the reasons, excellent characteristics of the solid state imaging device are provided which are free form image inferiority caused by flicker, shading, dust and so forth.

This application is a continuation of application Ser. No. 08/311,694,filed on Nov. 21, 1994, now abandoned, which was a divisional ofapplication Ser. No. 08/132,386, filed on Oct. 6, 1993, now U.S. Pat.No. 5,404,005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to solid state imaging devices carryingcolor filters on a top surface of light-receiving sections formed, andmanufacturing method thereof.

2. Description of The Related Prior Art

Conventional ways for manufacturing color filters have been dyeing,printing, electro-plating or the like. Dyeing has been widely used, dueto its high resolution on color filter patterns and its dyestuff whichfacilitate attaining a desired photospectrograph. There are twodifferent methods to mount the color filters on the solid state imagingdevice: an on-wafer method and a filter bonding method. In particular,the on-wafer method, which enables the color filters to be mounteddirectly on a substrate of the solid state imaging device, has beenconsidered as the mainstream in the field. Keeping these points in mind,combination of the dyeing method and the on-wafer method as mentionedabove (referred to hereinafter as the on-wafer dyeing method) is used toform the solid state imagining device with color imaging function.

A description is given below of the solid state imaging device and themanufacturing method thereof featuring the on-wafer dyeing method, withreference of accompanying drawings.

FIG. 33 shows the structure of a prior art solid state imaging device.On a surface of a semiconductor substrate 1, an array of photodiodes orlight-receiving sections 2 are arranged at given positions. Aninsulating layer, transfer electrodes and light-shielding layers areformed on each of transfer sections in the area of the surface of thesemiconductor substrate 1 excluding the light receiving sections 2. Thesurface of the semiconductor substrate 1 is covered with a protectinglayer 5. A transparent flattening layer 6 is formed to cover the wholeprotecting layer 5. Thereafter, color filters 7 are formed. The colorfilters 7 consists of three different colors: red color filters 7R,green color filters 7G and blue color filters 7B. Bonding pads 3 andscribe lines 4 are formed at an edge portion of the semiconductorsubstrate 1 of the solid state imaging device.

In forming the color filters 7, the material which is made by combiningnatural protein such as gelatin or casein and dichromate as aphoto-sensitizer with water as a solvent, is evenly applied on thesurface of the transparent flattening layer 6 mounted on the protectinglayer 5, and then, ultraviolet rays are radiated via desired masks onthe material. The unirradiated areas against the ultraviolet rays isdissolved into water to create color filter patterns. Then, the colorfilter patterns are colored with the dyestuffs containing a desiredphotospectrography to form the color filter 7. Finally, it is followedby the removal of the transparent flattening layer 6 disposed on thebonding pads 3 and the scribe lines 4 which are used for external lineconnection of the solid state imaging device. Through all the processesdescribed above, color filters 7 are completed.

In keeping with downsizing of chip size and higher number of pixels, itis generally required to reduce the size of the light-receiving sectionsincluded in the solid state imaging device. To achieve this, the colorfilters 7 need to be minimized. In this instance, it is necessary tomake uniform the shape and the photo spectrography of the color filters7. However, the material made by combining natural protein such asgelatin or casein with dichromate as photo sensitizer, which have beenso far employed for the color filters, have a low resolution ofpatterning. Therefore, it makes the quality of the solid state imagingdevice carrying the color filters 7 different from device to device. Inan attempt to pursuit minuter patterns than the resolution of thematerial regardless of the flatness of the surface of the solid stateimaging device, the color filters 7 are formed with curvature like thepupil as shown in FIG. 33. Consequently, the color filters 7 areoverlapped at the edge portions thereof with the adjacent ones, even ifflatness on the surface of the solid state imagining devices is madehigher. The light traveling through the overlapped parts, therefore,produces irregular image such as mixed color or flickers. Besides, theshape of the surface in the color filters 7, which is curved but notflat, causes the photo spectrography in each of pixels to vary. As aconsequence, poor characteristic such as flickers or irregular shadingare observed in the solid state imaging device.

The distribution of molecular weight in the natural protein is, even ifprecisely refined, is hard to be make uniform with high reproducibility.In addition, the natural protein contains an alkali metal such as Na orK of as much as several thousands ppm, which diffuses in the solid stateimaging device and increases dark current. Especially in the solid stateimaging device, particular pixels with bigger dark current than thesurrounding pixels show up as white dots on the picture, which causeswhite blemish to appear in several weeks after manufacturing the solidstate imaging device.

To solve these problems, it is proposed to use a syntheticphotosensitive material which have high resolution in Japanese Laid-openpublications Nos. 1-142605, 2-96704, 4-163552 and others. According tothose publications, synthetic photosensitive materials are synthesizedby dissolving a copolymer containing dyeing radicals and aphotosensitizer into an organic solvent. According to those methods,color filters are formed by applying the synthetic photosensitivematerials, then exposing the materials to ultraviolet rays, anddeveloping the unexposed portions with the organic solvent or a watersolution containing the organic solvent as a developer.

In general, if the synthetic photosensitive materials employing theorganic solvent are applied to the transparent flattening layers forforming color filters on the surface of the solid state imaging device,transparent flattening layers 6 may be dissolved into the organicsolvent so that mixed layers may be formed between the transparentflattening layers 6 and the color filter layers. In this process, afterthe color filter layers are formed and patterned, it is impossibleremove the mixed layers formed in the unexposed areas. Accordingly, whenthe first of the color filters 7 are formed, the mixed layers experienceundesired coloring. Furthermore, when the second or the third colorfilter 7 are formed, the mixed layers colored during disposition of thefirst color filters 7 still remain at the interface between the secondor the third color filters 7 and transparent flattening layers 6.Accordingly, mixed color appears to invite problems leading to inferiorpictures such as flickers.

Speaking the conventional method in more detail, in order to remove thetransparent flattening layers 6 mounted on the bonding pads 3 and thescribe line 4, dry etching such as O₂ using oxygen plasma is employed.This method produces more particles than the method of removal throughexposure and development techniques. Besides, dark current increase dueto plasma damage, which in turns causes white blemish. This method,however, provides extremely higher uniformity in thickness of the layerthan the conventional method which uses the material a consisting ofnatural protein and a dichromate. It follows that the shape of the colorfilters are made considerably uniform. As a consequence, the method offorming the color filters through the use of the syntheticphotosensitive materials with the organic solvent, is more and moreeffective as imaging elements in the solid state imaging device becomesmaller and smaller, because of its higher degree of controllability onpatterns.

Thus, irregular or deformed patterns on the color filters 7 deterioratethe characteristics of the solid state imaging device, whereas themethod of using the synthetic photosensitive materials for the colorfilters may solve the above discussed problems but faces another problemof inferior images caused by flickers, particles, white pecks and thelike.

Keeping those problems in mind, the present invention is to provide asolid sate imaging device with excellent imaging performance andcharacteristics, while meeting the demand for downsizing of chip sizeand a higher number of pixels in the solid state imagining device.

SUMMARY OF THE INVENTION

To solve the problems described above, an embodiment of the presentinvention provides a solid state imaging device which comprises asubstrate having at least light receiving sections and charge transfersections, a transparent gap filler layer and a transparent flatteninglayer mounted on the substrate and color filters of syntheticphotosensitive material on the transparent flattening layers.

To solve the problems described above, another embodiment of the presentinvention provides a method of manufacturing a solid state imagingdevice which comprises the steps of: preparing a substrate having atleast light receiving sections and charge transfer sections; forminglight-shield material on the charge transfer sections; covering thelight receiving sections and the charge transfer sections with aprotecting layer; forming a transparent gap filler layer ofphotosensitive thermosetting material on the protecting layer in thelight receiving sections; forming a transparent flattening layer ofphotosensitive thermosetting materials on the transparent gap fillerlayer and the protecting layer in the charge transfer sections; andforming color filters of synthetic photosensitive material with a watersolvent, on the surface of the transparent flattening layers.Preferably, the color filters may be formed through light exposure anddevelopment techniques.

To solve the problems described above, still another embodiment of thepresent invention provides a method of manufacturing a solid stateimaging device which comprises the steps of: preparing a substratehaving at least light receiving sections and charge transfer sections,said substrate further having bonding pads for external connection ofthe solid state imaging device and a scribe line for separation of thesolid state imaging device into individual solid state imaging units;forming light-shield material on the charge transfer sections; coveringthe light receiving sections and the charge transfer sections with aprotecting layer; forming a transparent gap filler layer of positivetype photosensitive thermosetting material on the protecting layer inthe light receiving sections; forming a transparent gap filler layer ofphotosensitive thermosetting material in the scribe line and in thebonding pads; forming a transparent flattening layer of photosensitivethermosetting materials on the transparent gap filler layer and theprotecting layer in the charge transfer sections; forming color filtersof synthetic photosensitive material with a water solvent, on thesurface of the transparent flattening layers; and removing the gapfiller layer and the transparent flattening layer from the scribe lineand the bonding pads. Preferably, the color filters may be formedthrough radiation exposure and development techniques. The gap fillerlayer and the transparent flattening layer in the scribe line and thebonding pads may be removed through radiation exposure and developmenttechniques.

In still another aspect of the present invention, a method ofmanufacturing a solid state imaging device comprises the steps of:preparing a substrate having at least light receiving sections andcharge transfer sections, said substrate further having bonding pads forexternal connection of the solid state imaging device and a scribe linefor separation of the solid state imaging device into individual solidstate imaging units; forming light-shield material on the chargetransfer sections; covering the light receiving sections and the chargetransfer sections with a protecting layer; forming a transparent gapfiller layer on the protecting layer in the light receiving sections;forming another gap filler layer of photosensitive thermosettingmaterial in the scribe line and in the bonding pads; forming atransparent flattening layer of non-photosensitive thermosettingmaterials on the transparent gap filler layer and the protecting layerin the charge transfer sections; carrying out heat treatment on thetransparent flattening layer; forming color filters of syntheticphotosensitive material with an organic solvent, on the surface of thetransparent flattening layers; and removing the gap filler layer in thescribe line and the transparent flattening layer on the bonding pads.

In still another aspect of the present invention, a method ofmanufacturing a solid state imaging device comprises the steps of:preparing a substrate having at least light receiving sections andcharge transfer sections, said substrate further having bonding pads forexternal connection of the solid state imaging device and a scribe linefor separation of the solid state imaging device into individual solidstate imaging units; forming light-shield material on the chargetransfer sections; covering the light receiving sections and the chargetransfer sections with a protecting layer; forming a transparent gapfiller layer on the protecting layer in the light receiving sections;forming another gap filler layer in the scribe line and in the bondingpads; forming a transparent flattening layer of negative typethermosetting materials on the gap filler layers and the protectinglayer in the charge transfer sections; carrying out heat treatment orradiation exposure or both on the transparent flattening layer; formingcolor filters of synthetic photosensitive material with an organicsolvent, on the surface of the transparent flattening layers; andremoving the gap filler layer in the scribe line and the transparentflattening layer on the bonding pads.

The above-mentioned synthetic photosensitive material used in thepresent invention, contains an extremely few amount of alkali metal inits resins and photosensitizer, so that the material is of higherquality as material for color filters, compared with the conventionalmaterial made from the natural protein and the dichromate. The syntheticphotosensitive material is remarkably slow in dark reaction, so thatchange in the characteristics with passage of time is a minimum.

The color filter material of the present invention exhibits an excellentresolution of patterning due to the photosensitizer selected, ascompared with the material of the natural protein with the dichromate.Besides, although the synthetic photosensitive material with a watersolvent is used to form color filters, the appearance of particles andwhite blemish caused by plasma damage is suppressed down, becauseetching method is not used in order to remove the transparent flatteninglayers formed on surfaces of the bonding pads and the scribe lines.

Consequently, the present invention makes it possible to form colorfilters with highly uniform shape and spectral characteristics on thefinely flattened surface of the semiconductor substrate, while meetingthe demand for downsizing and a higher number of pixels in the solidstate imaging device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectional view of structure in a solid state image devicein a first embodiment of the present invention.

FIG. 2 shows a sectional view of a manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 3 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 4 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 5 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 6 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 7 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 8 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 9 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 10 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 11 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 12 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 13 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the first embodiment of thepresent invention.

FIG. 14 shows curves of transmission of acrylic copolymer-diazo compoundwith respect to the wavelength of light.

FIG. 15 shows curves of transmission of acrylic copolymer-diazo compoundwith respect to the wavelength of light.

FIG. 16 shows curves of transmission of acrylic copolymer-diazo compoundwith respect to the wavelength of light.

FIG. 17 shows a sectional view of a manufacturing method of a solidstate imaging device in accordance with a second embodiment of thepresent invention.

FIG. 18 shows a sectional view of a manufacturing method of a solidstate imaging device in accordance with a third embodiment of thepresent invention.

FIG. 19 shows a sectional view of structure of the solid state imagedevice in the second embodiment of the present invention.

FIG. 20 shows a sectional view of a manufacturing method of a solidstate imaging device in accordance with a fourth embodiment of thepresent invention.

FIG. 21 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 22 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 23 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 24 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 25 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 26 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 27 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 28 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 29 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 30 shows a sectional view of the manufacturing method of the solidstate imaging device in accordance with the fourth embodiment of thepresent invention.

FIG. 31 shows a sectional view of a manufacturing method of the solidstate imaging device in accordance with a fifth embodiment of thepresent invention.

FIG. 32 shows a sectional view of a manufacturing method of the solidstate imaging device in accordance with a sixth embodiment of thepresent invention.

FIG. 33 shows a view of structure in a solid state imaging device ofprior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A description will be given of a solid state imaging device inaccordance with preferred embodiments of the present invention withreference to the accompanying drawings.

FIG. 1 shows a structure of a solid state imaging device in a firstembodiment of the present invention. The following will discuss a methodof forming a color filter with a water-soluble, negative type syntheticphotosensitive material employing water which contains a solvent and adeveloper and water. The color filters are patterned by means ofradiation exposure and development techniques.

On a surface of a P-type semiconductor substrate 8, there are formedN-type light-receiving sections 9 of the solid state imaging devicewhich includes a plurality of solid state imaging units consisting of anumber of imaging elements. At the periphery of the solid state imagingdevices on the semiconductor substrate 8 there are formed scribe lines10 which enables those imaging units to be cut and separated off theadjacent units. The bonding pads 11 are formed near the scribe lines 10.

It is noted that the semiconductor substrate 8 has electric chargetransfer sections 12 in addition to the light receiving sections. On asurface of the electric charge transfer sections 12 located between twoadjacent light-receiving sections 9 on the semiconductor substrate,there are mounted double layer type transfer electrodes 13 with aninsulating layer 14 such as SiO2 inserted between the two electrodes.Also, light-shielding metal layers 15 are disposed on a top surface ofthe transfer electrodes 13 to prevent external light from entering theelectric charge transfer sections 12. Besides, protecting layers 16containing SiO₂ are formed on a surface of the light-shielding metallayers 15 and the insulating layer 14.

The level difference or gap between the scribe lines 10 and theprotecting layers 16 mounted on the insulating layer 14 is 1.5 thru 2.0μm, and a gap between protecting layers 16 above the light-receivingsections 9 and the other protecting layers 16 on the light-shieldingmetals layers 15 is 0.8 through 1.5 μm.

In this case, if an attempt is made to apply the material so as to formcolor filters 19 on the light-receiving sections 9 directly, a resistmaterial caught by the gaps causes uneven application of the material asif tails were left, thereby resulting in failure to form the colorfilters 19 with uniform shape.

To solve the above problems, transparent gap filler layers 17 are formedabove the light-receiving sections 9 to make it as high as theprotecting layers 16 mounted on the light-shielding metals 15.

Also, in order to minimize the gap between the transparent gap fillerlayers 17 and the protecting layers 16 on the light-shielding metal 15and flatten the working surface of the solid state imaging device withhigher precision, a transparent flattening layer 18 is formed on a topsurface of the transparent gap filler layers 17 and the protectinglayers 16. Both of the transparent gap filler layers 17 and thetransparent flattening layers 18 are formed from the materials which arehardened with heat and positive type photosensitive (referred tohereinafter as the positive type photosensitive thermosetting material).

On the flattening layer 18, color filters 19R, 19G and 18B of red, greenand blue are formed to provide the solid state imaging device with colorfunction. Whereas in the drawings the color filter of 19R, 19G, and 19Bare arranged at intervals, shading may occur when light travels throughthe light-receiving sections in which the color filters are not mounted.It is, therefore, preferable to reduce the interval between the colorfilters a minimum or zero. The color filter 19R, 19G, and 19B arepositioned facing the light-receiving sections respectively. With theabove arrangement, a single color light impinges on each of thelight-receiving sections. According to the present invention, thesecolor filters 19 are made of a synthetic photosensitive material whichcontains water as a solvent and a developer.

A manufacturing method of the solid state imaging device in accordancewith the first embodiment of the present invention is discussed,referring to FIG. 2 through 13.

As shown in FIG. 2, the light-receiving sections 29 are formed by dopingan N-type impurity from desired positions on a P-type semiconductorsubstrate 28 of silicon or the like. On a surface of an insulating layer34 deposited on the semiconductor substrate 28, bonding pads 31,transfer electrodes 33, and light-shielding metal layers 35 are formed.Protecting layers 36 are also formed on a surface of the light-shieldingmetal layers 35 and the insulating layers 34.

Then, as shown in FIG. 3, in order to fill the largest gap in the solidstate imaging device located between the top surface of thesemiconductor substrate 28 in scribe lines 30 and the protecting layers36, a gap filler layer 40 is formed by means of rotary application. Thegap filler layer 40 is rotationally applied up to the same level as thesurface of protecting layers 36. Heat treatment is followed for a fewminutes at a temperature of 200° C. or higher so as to evaporate asolvent contained in the material and harden the gap filler layer 40.All of the portions excluding the gap on the scribe line 30 are removedby means of radiation exposure and development.

The reason why the gap filler layer 40 is formed in the scribe line 30is, as seen from the drawings, to flatten the surface of the solid stateimaging device by filling rugged surfaces of the substrate due to thedisposition of the transfer electrodes 33 and due to the formation ofthe scribe lines 30. In this case, the gap in the scribe line 30 islarger than that due to the transfer electrodes 33. Accordingly, if anattempt is made once to flatten all of the unevenness of the substratesurface by rotary application, the resist material would have gottencaught by the scribe line 30 having the larger gap, resulting in unevenor irregular application like tails left.

Therefore, these gaps need to be filled in separate processes. Therugged surface in the scribe line 30 is first be flattened. The wholegap filler layer 40 is to be removed at a time in a final step of themanufacturing process along with a polymer mounted on the scribe line 30and the bonding pads 31 through the radiation exposure and developmenttechniques. To this end, positive type photosensitive thermosettingmaterial is used for the gap filler layer 40. However, the gap fillerlayer 40 does not need to be colorless and transparent in a visiblelight range, it is mounted in the scribe line 30 and to be removed inthe final step.

In the above illustrated embodiment, a typical example of the positivephotosensitive thermosetting material may include polyglycidylmethacrylate and polymethyl methacrylate as its basic structure. Ethylcellosolve acetate is used as a solvent. Polymethyl methacrylate, whenirradiated with far ultraviolet rays like Deep-UV, experiences principalchain scission. Thus, this material shows positive type characteristics.However, it shows low sensitivity to G-rays or I-rays, which is notsuitable for patterning.

As shown in FIG. 4, in order to fill the gaps between protecting layers36 on the insulating layer 34 and the other protecting layers 36 on thelight-shielding metal layer 35, the transparent gap filler layers 37 arerotationally applied up to the same level as the surface of theprotecting layers 36 on the light shielding metal layers. Heat treatmentis followed for a few minutes at a temperature of 200° C. or higher. Theentire transparent gap filler layers 37 except the portions thereof inthe gaps is removed by means of exposure and development. Thetransparent gap filler layers 37 thus formed above the light-receivingsections 29 need to be colorless and transparent in the visible lightrange. In the illustrated embodiment, the material employed for the gapfiller layer 40 is nevertheless colorless and transparent in the visiblelight range as shown in FIG. 3. The transparent gap filler layers 37,therefore, include the same as the positive type photosensitivethermosetting material employed for the gap filler layer 40.

The other gaps in the imaging units in the solid state image device areall treated in the same process as shown in FIGS. 3 and 4, or will betreated in the same manner as another separate step.

In the next process, as shown in FIG. 5, in order to bring gaps betweenthe gap filler layer 40 and the transparent gap filler layers 37 withrespect to the protecting layer 36 into agreement, both of which areformed in the process shown in FIGS. 3 and 4, a transparent flatteninglayer 38 of a single layer or multiple layers is formed by rotaryapplication. This flattening layer makes the overall surface of thesolid state imaging device flat and free from unevenness. After rotaryapplication of the material for the transparent flattening layer, heattreatment is carried out for a few minutes at a temperature of 200° C.or higher to evaporate a solvent contained in the material. The materialused for the transparent flattening layer 38 in this process is the sameas the positive type photosensitive thermosetting material used for thegap filler layer 40 and the transparent gap filler layers 37 in theprocess described above.

The manufacturing steps shown in FIG. 2 through FIG. 5 flatten the gapsbetween the protecting layers 36 mounted on the light-shielding metallayers 35, the protecting layers 36 covering the insulating layers 34,and a top surface of the semiconductor substrate 28 in the scribe line30, thereby minimizing the overall gap in the solid state image deviceto 0.1 μm or lower.

The next step, as shown in FIG. 6, is to form a color filter base layer41 on the surface of the transparent flattening layer 38a by means ofrotation application employing synthetic photosensitive material to beas thick as approximately 0.3 through 1.0 μm. Heat treatment is followedat a temperature of 70° C. through 100° C. for a few minutes in order toevaporate a solvent contained in the material. In the process as shownin FIG. 6, it is possible to form the color filter base layer 41 withperfect flatness by rotationally applying the synthetic photosensitivematerial of highly uniform applicability on the finely flattenedtransparent flattening layers 38a.

Then, as shown in FIG. 7, the color filter base layer 41 is exposed toI-rays with desired photo mask patterns. The amount of I-rays radiatedwas 100 through 200 J/cm.

Subsequently, as shown in FIG. 8, the portion of the color filter baselayer 41 which is not with ultraviolet rays is soaked in water as adeveloper for one minute to be dissolved. After dissolution is over, thedeveloper is removed and heat treatment is effected for a few minutes ata temperature of 130° through 150° C. The temperature in excess of 150°C. would make it harder for dyestuffs to penetrate the color filer 41.Otherwise, the temperature below 130° C. would make it easier for thedyestuffs to come in but the dyestuffs would make patterning rough. Theprocesses described above leads to the formation of a color filterpattern 42.

In the next step, as shown in FIG. 9, the finished color filter pattern42 are soaked in the dyestuffs and then washed and dried. Dyeing takesplace by coupling dying radicals included in the color filter pattern 42and the dyestuffs, thus creating a color filter 39. In the illustratedembodiment, amino radicals contained in the material are used for dyeingradicals to be discussed in detail later. In connection with thedyestuffs, azo dyestuffs are used for red, xanthene dyestuffs foryellow, and phtalocyanine dyestuffs for blue, respectively.

Once the color filter 39 has been formed, if treated by the fixingmethod, it will never be mixed with other dyestuffs when being soaked indyeing liquid in the next dyeing step, as long as a fixing technique iscarried out. This fixing technique, for example, is performed by soakingthe color filter in an aqueous tannin acid solution and then in anaqueous antimony potassium tratrate solution at a water temperature of40° C. for a couple of minutes, respectively.

The next step, as shown in FIG. 10, is to form second and third colorfilters 39. The above sequence of the steps of FIG. 6 through FIG. 10 isrepeated.

The embodiment illustrated in shown in FIG. 6 through FIG. 10 employsthe so-called fixing technique, by which the color filter 39 is fixedand hardened after being formed. Alternative approaches to form colorfilters are a dye-preventing layer method (or a protecting layer method)by which to form dye-preventing layers every time after forming thecolor filters 39, and a window method by which a color filter pattern 42is formed uniformly on the transparent flattening layer 38 and atransparent film to protect from color mixture is formed with a windowopened for a desired color filter pattern 42 to be dyed.

If the material made of natural protein such as gelatin or caseincombined with a dichromate as a sensitizer are employed in the steps ofFIG. 6 through FIG. 10, a considerable timewise change would have beenobserved due to dark reaction during the formation of the color filter.In this instance, even if the steps of application, exposure,development, and dyeing are controlled exactly in terms of minutes, itwould be impossible to form the color filter 39 on the solid stateimaging device uniformly.

On the other hand, diazo compounds which are employed for the syntheticphotosensitive material are considerably slow in timewise or agingchange, compared with the dark reaction of the material consisting ofthe dichromate and natural protein, and hardly experience timewisechange during the manufacturing of the color filter 39. Accordingly, thecolor filer 39 of a single color formed in the solid state imagingdevice may enjoy excellent uniformity of shape in the solid stateimaging device. Moreover, dyeability of the color filter will not changeeven with change in the material.

For the reasons described above, the color filter 39 of a single colorcarried on the solid state imaging device through the steps of FIG. 6 toFIG. 10 is highly uniform both in shape and photo spectrography.Therefore, the solid state imaging device is very satisfactory in termsof shading which is caused and affected by irregularity in shape ordispersion of photo spectrography. Whereas flicker characteristics ofthe conventional color filter of the natural protein and the dichromateshow 8 degrees, the color filters formed in the illustrated embodimentof the present invention show 0 through 2 degrees, which meanssignificant improvement in characteristics. While shadingcharacteristics of the conventional color filter point 20 through 30 mV,the illustrated embodiment of the present: invention point 15 mV, whichis also improvement in characteristics. It is noted that 0 stands forthe ideal characteristics both in flicker and shading characteristics.

In the step of FIG. 6, however, if a synthetic photosensitive materialwith an organic solvent is applied on the transparent flattening layer38a, the transparent layer 38a may be dissolved into the organic solventto create a mixed layer of the two materials between the transparentflattening layer 38a and the color filter base layer 41. This is becausethe positive type photosensitive thermosetting materials for thetransparent flattening layer is low in hardness of film and inresistance to organic solvent.

Even in the above illustrated embodiment, polyglycidyl methacrylate usedfor the transparent flattening layer 38 may experience bridge formationwhen heat treatment is carried out. Polymethyl methacrylate is, however,slower in bridging reaction due to heat treatment than polyglycidylmethacrylate. Accordingly, polymethyl methacrylate, which is compoundedto secure positive type of sensitivity for far ultraviolet rays, lowersfilm hardness and resistance to organic solvent.

Therefore, in the case where the color filter layer 41 is formed asshown FIG. 6 and then the color filter pattern 42 is formed by means oflight exposure, development, and heat treatment as shown in FIGS. 7 and8, it is impossible to remove the mixed layer developed at thenon-exposed areas. Accordingly, when the first color filter 39 is formedin the step of FIG. 9, the mixed layer is colored. Thereafter, when thesecond or the third color filter 39 is formed in the step of FIG. 10,the mixed layer which is colored during the formation of the first colorfilter 39 still remains in the interface between the second or the thirdcolor filter 30 and a transparent flattening layer 38a. Therefore, colormixture takes place to cause inferior picture including flickers.

However, the present invention employs the material with water as asolvent and a developer for the synthetic photosensitive material, sothat the transparent flattening layer 38a is not dissolved with thecolor filter material, which prevents a mixed layer from being formed.The present invention overcomes problem of inferior image with colormixture caused by the mixed layer colored.

After all the color filters 39 are formed as shown in FIG. 11, a secondtransparent flattening layer 38b is formed on a top surface of the colorfilters 39 by means of rotary application. The heat treatment isfollowed at a temperature of 200° C. or higher for a few minutes.

It is recognized that both the color filters 39 and the transparentflattening layer 38 are of organic material and excellent in adhesion.It implies that flatness is improved without a gap filler as shown inFIGS. 3 and 4. In case further improvement in flatness is desired, thetransparent flattening layers 38 may be repeatedly formed. In theillustrated embodiment, the transparent flattening layer 38 is formedtwice. As a result, a gap or level difference is minimized to less than0.1 μm by the second transparent layers 38. Subsequently, so as toelevate the sensitivity of the solid state imaging device, micro lens 43are formed on the surface of the second transparent flattening layer38b.

As shown in FIG. 12, in order to remove the gap filler layer 40 and thetransparent flattening layer 38a formed in the scribe line 30 and thetransparent flattening layer 38b mounted on bonding pads 31, the solidstate imaging device is exposed to far ultraviolet rays with photomasks.

Finally, as shown in FIG. 13, the gap filler layer 40 and thetransparent flattening layer 38 which have been exposed to farultraviolet rays are dissolved into a mixed liquid of methyl ethyketoneand isopropyl alcohol as a developer. The developer is removed afterdissolution, and heat treatment is followed at a temperature ofapproximately 150° C. for a few minutes. By this process, the gap fillerlayer 40 and the transparent flattening layer 38a formed in the scribeline 30, and the transparent flattening layer 38b mounted on the bondingpads 31 are removed all at a time.

The above steps of FIG. 2 through FIG. 13, complete the formation of anon-chip filter consisting of the color filters 39 and micro lens 43 overthe semiconductor substrate 28.

The time for formation of the layers and the time for evaporation of thesolvent are well balanced and the layers formed are even and free ofrugged surfaces where rotary application is used to form the layers at1000 through 5000 rotations per minute, through the use of the positivetype photosensitive thermosetting materials with an organic solventconsisting of alcohol group and cellosolve group in the steps of FIGS. 2through 5. In consequence, the gaps in the solid state imaging devicebetween the protecting layers 36 formed over the light-shielding metallayers 35, the protecting layers 36 on an insulating layer 34, and thetop surface of the semiconductor substrate 28 in the scribe line 30 aresuccessfully flatted with precision.

In the steps of FIGS. 12 and 13, the gap filler layer 40 and thetransparent flattening layer 38 formed on the scribe line 30, and thetransparent flattening layer 38 mounted on the bonding pads 31 areremoved. These steps prevent problem of uneven application which occursduring rotary application of the color filter material and also thinningof the color filter base layer 41 in the area where gaps are locatedclosely each other as shown in FIG. 6. Similarly, the micro lens 43formed may enjoy high uniformity of shape. Accordingly, the color filter39 and micro lens 43 both of which are formed on the flatly formed colorfilter base layers 41 show excellent uniformity in shape.

In the steps of FIGS. 12 and 13, the gap filler layer 40 and thetransparent flattening layer 38a in the scribe line 30 and thetransparent flattening layer 38b mounted on the bonding pads 31 areremoved by means of exposure and development, which prevents occurrenceof particles caused by dry etching, appearance of white blemish due toplasma damage, and thus inferior image. In case of etching with O₂, forexample, the dark current of the solid state imaging device increases byapproximately 3 through 6 mA under the etching conditions of 0.8 through1.2 Torr for gas pressure, 200 W for high-frequency electric power, 5through 5 minutes for etching time. However, the illustrated embodimentof the present invention does not experience increasing of dark currentdue to plasma damage or the appearance of white blemish, because of noetching method used.

A more detail description will be given of the color filters 39 employedin the above illustrated embodiment. The synthetic photosensitivematerial is used for the color filters 39. If the material of thenatural protein such as gelatin or casein compounded with dichromate asa sensitizer is used, a lot of problems would have come up due to thecharacteristics of the material used: treatment of dichromate used as asensitizer, dispersion of quality in natural protein, shortness ofperiod of preservation after the dichromate is added to the naturalprotein.

The natural protein is hard to be refined in quality with uniformity ofdistribution of molecular weight and high reproducibility. For instance,it is hard to control the difference in value of mean molecular weightbetween the materials to be as small as 30% or lower. The naturalprotein contains an alkali metal (for example, Na or K) of as much asseveral thousands ppm, which diffuses into the solid state imagingdevice and increases dark current. Especially, the pixels with largerdark current than the surrounding pixels in the solid state imagingdevice show up as white dots on the picture, which is one of causes ofwhite blemish. This also causes white blemish to appear in several weeksafter the manufacturing of the solid state imaging device.

In addition, the material of the natural protein with the dichromateshow non-Newtonian characteristics in which viscosity is not in directportion to power exerted on the material. Therefore, the value ofshearing stress which is set according to the number of rotations at thetime of rotary application becomes uneven and non-uniform, resulting indifficulty with uniform application of the layers. Furthermore, thenatural protein becomes deteriorated in patterning characteristics,dyeing characteristics and fixing characteristics due to heat.Accordingly, it is difficult to form the layers with high uniformity.The characteristics of the resulting color filter 39 in the solid stateimaging device are not satisfactory. In addition, the dichromate used asthe photosensitizer are harmful to human body and involves problemsincluding the need of special treatment with waste fluid for theenvironmental protection.

The synthetic photosensitive material used in the above illustratedembodiment exhibits not only both photo sensitivity and hydrophilicity(also hydrophobicity) but also dyeability with or without dyestuffs orpigments bonded or dispersed in the material. For instance, the materialmay be made dyeable by coupling the material with dyestuffs whichincludes dyeing power such as Quaternary ammonium salt.

The one actually employed in this embodiment is a dyeable syntheticphotosensitive material which is dissolved into water with a solvent of:

an acrylic copolymer consisting of 5-20 weight % of monomer as shown bythe following general formula within a range of mean molecular weightfrom 5000 to 100000 ##STR1## where R₁ represents a hydrogen atom or CH₃,R₂ and R₃ represent an alkyl group or allyl group such as CH₃, C₂ H₅, C₆H₅ and the like independently, and n represents an integer from 1 to 10;45-55 weight % of 2-hydroxy ethyl methacrylate; 20-30 weight % ofmethacrylic amide; and 5-10 weight % of benzylic methacrylate, and

oxy poly basic acid salt and a diazo compound.

Like the material of the natural protein compounded with dichromate asphoto sensitizer, this synthetic photosensitive material may bepatterned by way of water development. Therefore, the above material isfree of danger of toxicity, scent, and inflammability due to an organicsolvent. It is also safe to human body, because dichromate is notcontained in it. There is no need for special treatment with wastefluid, since a double salt such as sulfuric acid, sulfurous acid or thelike is used for the counter anion of diazo radicals in place of adouble salt such as zinc sulfide.

In addition, the acrylic copolymer provides the color filter 39 withsuperior durability, due to high film hardness, as compared with othersynthetic resin such as polyvinyl alcohol, novolak resin, vinyl familyresin or the like. The acrylic copolymer shows nearly 100% ofpermeability in the visible light range, with no possibility thatpermeability is lowered when heat treatment is repeated at a temperatureof 250° C. or more. In consequence, if the acrylic copolymer is usedwith the solid state imaging device, it allows more light to enter thelight-receiving sections 9 than other compound resins. As a result, thesolid state imaging device exhibits a highest sensitivity.

The acrylic copolymer used in the above embodiment may include, asacrylic monomer having dyeing performance as represented by the aboveformula, N, N-dimethyl amino methacrylate, N, N-dimethyl amino propylacrylate, acrylic acid diethyl amino ethyl, N, N-dipropyl amino ethylmethacrylate, N, N-dimethyl amino hexy methacrylate, or N, N-dimethylN-benzylic methacrylate. In this instance, if alkyl group or allyl groupincrease in the composition, swelling of pattern is a minimum whensoaked in dyeing liquid with no or less possibility of cracks.

2-hydroxy ethylmetha acrylate, which is a structural unit of the acryliccopolymer in the above embodiment, elevates adhesion with thetransparent flattening layer 38 and promotes the photo bridgingreaction. With a too small amount of 2-hydroxy ethylmetha acrylate,light-hardening ability is not sufficient. With a too large amount ofit, a number of gel are produced during the manufacturing of thecopolymer, leading to the production of so-called resist particles whichcause defects on the picture.

Methacrylic amide, which is another structural unit of the acryliccopolymer in the above embodiment, is required to dissolve the acryliccopolymer only with water and to dissolve (or develop) unexposedportions only with water. With a small amount of it, water developmentcan not be expected. With a large amount of it, increased swelling isobserved.

Benzylic methacrylate, which is another structural unit of the acryliccopolymer in the above embodiment, restrains the swelling during waterdevelopment. With a too large amount of benzylic methacrylate, the gelcontents of the acrylic copolymer increases.

Oxy poly basic acid salt, which is used for the synthetic photosensitivematerial in the above embodiment, acts as an assistant to dissolve theacrylic copolymer into water. An example of the oxy poly basic acid saltis malic acid or citric acid or the like.

The synthetic photosensitive material composed as described above showssmaller swelling due to water in the development process than solublesynthetic photosensitive materials of prior art. Accordingly, a highresolution of line-and-space of 1.5 μm wide can be observed in reliefpatterns, and the rate of residual film is 90% or more. The syntheticphotosensitive material, therefore, includes superior characteristics inresolution than casein or gelatin. As for dyeability, the material inthe above embodiment manifests dyeing and fixing characteristics to thesame extent to which gelatin shows a highest dyeability in the all kindsof the natural protein.

The above description is directed to examples of the color filtershaving dyeability themselves. In the following, description will begiven of an example to employ dyestuffs or pigments for providing thematerial with dyeability. The synthetic photosensitive material may becombined into coloring materials by bonding or dispersing dyestuffs orpigments having desired photo spectrography. With the coloringmaterials, the dyeing and fixing step of FIG. 9 can be eliminated.

In addition, the synthetic photosensitive material can be madewater-soluble or non-water-soluble, according to methods of combiningthe material components and choices of materials. Also, the syntheticphotosensitive material may be of the negative type light bridgeformation type including the natural protein compounded with thedichromate or of the positive type.

The synthetic photosensitive material with water for solvent, used inthe above embodiment, manifests the photo bridging type characteristics.As photo bridging type sensitizer, the diazo compounds and azidecompounds are known in addition to dichromate. The diazo compounds varyin sensitive wavelength range, heat stability, and choice ofbridge-formable polymers according to the structure thereof. It also canbe water-soluble or soluble to an organic solution by choosing the kindof a fellow anion. The azide compounds also vary in sensitive wavelengthrange, heat stability, and choice of bridge-formable polymers, accordingto the structure thereof. In addition, it shows a highestbridge-formability to non-water-soluble polymers.

Of all of the above materials, the diazo compounds show a higherbridge-forming efficiency for the water-soluble polymer for the colorfilters and provides high resolution of patterning. This shows superiorresolution of patterning, as compared to the color filter materials ofthe natural protein compounded with the dichromate. For a photosensitizer to be composed with the synthetic photosensitive materials,any kind of the diazo compound may be employed.

For example, one of the most effective negative type diazo compounds isa polycondensation product which consists of diphenylamine-4-diazoniumsalt or its derivative, and formaldehyde. It is noted that thediphenylamine 4-diazonium salt or its derivative containsdiphenylamine-4-diazonium salt and/or 3-methoxyl diphenylamine-4diazonium chloride. FIG. 14 shows change in permeability due to heattreatment in the case where the acrylic copolymer employed in the aboveembodiment is compounded with 4-diphenylamine sulfate formaldehydecondensation. In this case, a sudden drop of permeability was observedin the first 30 minutes of treatment time during the heat treatment at atemperature of 200° C. or higher. No further change is seen inpermeability during the succeeding heat treatment.

After a particular one of the color filter 39 is formed in the steps upto FIG. 10 for the formation of the on-chip filter on the solid stateimaging device, heat treatment is repeated in the step of forming thesecond transparent flattening layer and the micro lens 43 as shown inFIG. 11, in the step of removing the transparent flattening layer 38 andthe gap filler layer 40 in the scribe line 30 and the bonding pads 31shown in FIG. 12 through FIG. 13, and subsequently to the formation ofthe color filters 39. Once the on-chip filter has been formed, thespectral characteristics of the color filters 39 will not change despiterepeated heat treatment. The color filters in the solid state imagingdevice are thus free from coloring, irregular patterns, nor roughsurface due to heat treatment, with help of the diazo compounds composedin the synthetic photosensitive material. Accordingly, the thermalresistance need not be considered.

The characteristics of the solid state imaging device may be enhanced bychoosing a diazo compound which does not experience a decrease intransmission due to heat treatment. A typical example thereof is apolycondensation product consisting of diphenylamine-4-diazonium salt orits derivative, and 4.4'-bis-methoxylemethyl diphenylether. It is to benoted that the diphenylamine-4-diazonium salt or its derivative containsdiphenylamine-4-diazonium salt and/or 3-methoxyldiphenylamine-4-diazonium. FIG. 15 represents a big difference intransmission when a condensation product consisting ofdiphenylamine-4-diazonium salt or its derivative 4.4'-bismethoxylmethyldiphenylether is used in place of the 4-diazo diphenylamine sulfateformaldehyde condensation product. In this case, there is no bigdifference in time to stabilize photo spectrography from the beginningof heat treatment, as compared with the 4-diazo diphenylamine sulfateformaldehyde condensation product used. While the 4-diazo diphenylaminesulfate formaldehyde condensation product changes up to 68% intransmission with heat treatment, the photo sensitizer condensed fromdiazo diphenylamine sulfate and 4.4'-bis-methoxylmethyl diphenyletherchanges only up to 88% with the same treatment and no change is observedwith the latter in photo spectrography after this point.

The coloring by the diazo compounds as shown above is due to couplingreaction of diazo radicals which are undissolvable against sufficientphoto bridging. Especially in the case of the aforementionedpolycondensation products consisting of 4-diphenylamine sulfateformaldehyde condensation products and 4.4'-bis-methdoxymethyldiphenlether, hydrogen radicals existing in phenyl radicals, which existonly at the ortho or meta position, do not affect the coupling reaction.Only the coupling reaction between unreacted diazo radicals and aminoradicals existing between phenyl radicals have an influence on coloring.

Consequently, in diphenylamine-4-diazonium salt or its derivative,transmission will not change due to heat treatment by bonding other thanamino radicals between phenyl radicals, as shown in FIG. 16. Someexamples of such bonding are as follows:

R₁ --(CH2)_(q) --R₁ (q is an integer from 1 to 5.)

R₁ --O--R₆ --O--R1 (R₆ is aryl containing 6 through 12 C-atoms.)

R₁ --O--R1

R₁ --S--R₁ (R₁ is at least a phenyl radical)

As shown above, in the case where the diazo compounds having a little orno decline in transmission due to heat treatment is used to form thecolor filters 39 carried on the solid state imaging device, the amountof light entering the light-receiving sections 29 through the colorfilters 39 increases. The acrylic copolymer compounded with the diazocompounds similarly shows approximately 100% of transmission and doesnot experience decline in transmission even with repeated heattreatment. As a consequence, the diazo compounds described above enablethe solid state imaging device to elevate its sensitivity by 10% ormore.

FIG. 17 shows a manufacturing method of the solid state imaging devicein accordance with a second embodiment of the present invention. Themanufacturing steps in the first embodiment until each color filter 39of red, green and blue is formed are applicable to the secondembodiment. In the second embodiment, black stripes or light-shieldfilter 44 are formed to cover the areas where the color filters 39 arenot placed, in order to restrain so-called stray light from enteringeach light-receiving sections 29 through the areas. This arrangementimproves imaging characteristics and eliminates smear or flare. Theblack stripes 44 are also made of the synthetic photosensitive materialof black color using water for a solvent. This material enables theblack stripes to be uniform and excellent in shape or topography, ascompared with conventional stripes 44 which are made by compounding thenatural protein with the dichromate. In the conventional device, theedges of patterns are dull so that the black stripes may cover the lightreceiving sections. However, this embodiment of the present inventioneliminates such possibility. Accordingly, the solid state imaging deviceaccording to this embodiment achieve higher sensitivity.

FIG. 18 shows a manufacturing method of the solid state imaging devicein accordance with a third embodiment of the present invention. Thisembodiment shows a way of forming color filters 39MG, 39CY, 39GR, and 39YE of magenta, cyan, green, and yellow in place of forming the colorfilters 39 of the three primary colors of red, green, and bluerespectively. In this example, green color is produced by combiningyellow and cyan.

This method also enables to form color filters with uniformity both inshape and photo spectrography and the sold state imaging device withsuch color filters exhibits excellent characteristics free of shading,flickers, color-mixture, white specks, and so forth.

The synthetic photosensitive materials including water as a solvent inthis embodiment does not form a mixed layer with any transparentflattening material including organic solvents. In addition to thepositive photosensitive thermosetting material, non-photosensitivethermosetting materials which are hardened by heat treatment andnegative type materials which are hardened with heat treatment and shownegative sensitivity (called the negative photosensitive thermosettingmaterial) may be used in the above embodiment.

Referring to FIGS. 19 through 32, a description will be given of a solidstate imaging device which is formed of negative synthetic materialincluding an organic solvent as developer through drying etching, and amethod of manufacturing the same.

In these embodiment, excellent uniformity on the surface is achieved byapplying color filter material on the surface of a transparentflattening layer through the use of an organic solvent with excellentvolatility. Where the material of natural protein and dichromate isapplied to form a color filter of thickness of 0.7 μm on a wafer of 6inches, variation in layer thickness (maximum-minimum) shows 0.08through 0.10 μm. On the contrary, where the synthetic photosensitivematerial of water solubility is used, the variation is improved in theorder of only 0.01 through 0.02 μm. Furthermore, where the syntheticphotosensitive material includes an organic solvent, a highestuniformity in flatness is achieved in the order of less than 0.005 μm.Accordingly, the above material is excellent in controllability onpatterning and dyeing characteristics.

FIG. 19 shows a structure of a color solid state imaging deviceaccording to another embodiment of the present invention. Asemiconductor substrate 51 is P-type and light-receiving sections 52 areN-type in the solid state imaging device. The device also includebonding pads 53 and scribe lines 54. Double-layer transfer electrodes 56with an insulating layer 56 such as SiO₂ are disposed on each surface ofelectric charge transfer sections 55 located between the adjacentlight-receiving sections 52 on the semiconductor substrate 51.Light-shielding metal layers 57 are formed to cover the surfaces of thetransfer electrodes 56 to prevent the external light from entering theelectric charge transfer sections 55.

The gap between the scribe line 54 and the protecting layers 56 mountedon the insulating layer is 1.5-2.0 μm, and the gap between protectinglayers 56 above the light-receiving sections 52 and the other protectinglayers 56 on the light-shielding metal layers 57 is 0.8 through 1.5 μm.Under the circumstance, a resist may get caught by the gaps and causesuneven application just like tails left in applying the material abovethe light-receiving sections directly to form color filter 61, so thatcolor filters 61 are not formed into uniform shape. Transparent gapfiller layers 59 are formed on the light-receiving sections 52 to maketop surfaces of the light-receiving sections flush with thelight-shielding metal layers 57. In order to smooth the gap between thetransparent gap filler layers 59 and the light-shielding metals 57 withhigher precision, a transparent flattening layer 60 is formed on thesurface of the transparent gap filler layers 59 and the light-shieldingmetal layers 57. This transparent flattening layer 60 is made ofnon-photosensitive thermosetting material or negative typephotosensitive thermosetting material. Color filters 61R, 61G and 61B ofred, green, and blue are formed on a surface of the transparentflattening layer 60 to provide the imaging device with color function.The color filters 61 are positioned facing each of the light-receivingsections. Accordingly, each of the light-receiving sections receivesmonocolor light.

The synthetic photosensitive materials as described in the first throughthird embodiments are used for the color filters 61. The syntheticphotosensitive materials are prepared by bonding or dispersing materialshaving functions necessary for the color filters 61. For instance, thematerials may be made dyeable by combining materials which couple withdyestuffs, such as Quaternary ammonium salt. The materials may containcoloring material by bonding or dispersing dyestuffs or pigmentssuitable for desired photo spectrography. It is generally known that thenatural protein is a water-soluble polymer and photo sensitizers to becombined into the natural protein are limited to cross-link type such asdichromate acid salts, diazo compounds, and azide compounds. Especially,each of the light-receiving sections 21 in the solid state imagingdevice is as small as a few μm, so that only the dichromate salt out ofthe above listed synthetic photosensitive materials may be used in orderto secure satisfactory resolution. However, the synthetic photosensitivematerials can be water-soluble or non-water-soluble, according tomethods of combining the components and choice of the componentmaterials. The synthetic photosensitive materials may be either of thenegative type of light cross-link containing the natural protein and thedichromate or of the positive type.

In particular, the time for formation of the layers and the time forevaporation of the solvent are well balanced and the layers formed areeven and free of rugged surfaces where rotary application is used toform the layers at 1000 through 5000 rotations per minute, through theuse of the photosensitive materials with an organic solvent consistingof alcohol group or cellosolve group out of the above describedcombination of the solvents.

The color filter materials used in the above embodiment are dyeable withcombination of material which may bind with dyestuffs and of thenegative type of synthetic photosensitive material with the organicsolvents. The structure of the materials is an acrylic copolymerincluding hydroxy ethyl methacrylate and dimethyl amino methacrylate asits fundamental component. In order to facilitate cross-link, azidecompounds are combined, which cross-link the acrylate exposed to I-rays.Ethylcellosolve is employed as a solvent.

A description will be now given of a manufacturing method of a solidstate imaging device in accordance with a fourth embodiment of thepresent invention, with reference to FIGS. 20 through 30.

As shown in FIG. 20, a number of light-receiving sections 72 are formedby doping an N-type impurity into desired positions on a P-typesemiconductor substrate 71 of silicon or the like. Transfer electrodes76 and light-shielding metal layers 77 are formed on a surface of thesemiconductor substrate 71.

As shown in FIG. 20, in order to fill the largest gap in the solid stateimaging device located between scribe lines 74 and the light-shieldingmetal layers 77, a gap filler layer 78 is formed by means of rotaryapplication. The gap filler material is applied so as to make the levelof the filled and elevated light-shielding metal layers 77 flush withthe top surface of the gap filler layer 78. After the rotaryapplication, heat treatment is effected to evaporate a solvent containedin the material. All of the material except in the gap on the scribeline 74 and the light-shielding metal layers are removed.

In the case that a negative type photosensitive materials is used forthe gap filler layer 78, removal is done by exposing required areas tolight and developing the same. In the case that a positive syntheticmaterial is used, removal is done by exposing non-required areas tolight and developing the same. Furthermore, in the case that thematerial does not assume sensitivity, removal is done by means of a dryetching method such as O₂ ashing using an oxygen plasma.

The next step of FIG. 22 is to form a transparent gap filler layer 79 byrotary application to fill the gap between the light-receiving sections72 and the light-shielding metal layers 77. This step is same as thestep of FIG. 3 by which the gap between the above scribe lines 74 andthe light-shielding metal layers 77 is filled.

The other gaps in the solid state imaging device are treated in the sameprocess as shown FIGS. 21 or 22, or are treated by a separate step inthe same manner.

FIG. 23 illustrates that the gap filler layer 78 and the transparent gapfiller layers 79 formed in the steps of FIGS. 20 and 21 are not on thesame level as the light-shielding metal layers 77 and therefore theflatness of the working surface of the device is low. Accordingly, tomake even the gaps between the gap filler layer 78, the transparent gapfiller layers 79, and the light-shielding metal layers 77, a transparentflattening layer 80 is formed by rotary application so that the topsurface of the solid state imaging device is made completely flat. Afterthe transparent flattening layer 80 is rotatively applied, heattreatment is carried out to evaporate solvents contained in materials.This transparent flattening layer 80 is to be in touch with colorfilters. Therefore, in the case that color filter materials with anorganic solvent of strong solubility are applied in the following steps,the transparent flattening layers 80 may be dissolved in the organicsolvent, thereby forming a mixed layer between the transparentflattening layer 80 and color filter base layers.

For this reason, when the color filters are formed through heattreatment following the deposition of the color filter base layer 81,light exposure, development, and post-development heat treatment, it isimpossible to remove the mixed layer remaining in the unexposed areas.If dyeing process is carried out as it is, the remaining mixed layer isalso dyed. Accordingly, when the second or third color filter is formedafter the formation of the first color filter, the mixed layer coloredduring the formation of the first color filter still remains at theinterface between the second or the third color filter and theflattening layer 80. Consequently, color mixing takes place only tocause inferior picture.

For the reason as discussed above, the material for the transparentflattening layer is required to show excellent flatness of a layerresulting from rotation application thereof and exhibit such aresistance to the organic solvent in the color filter base layers thatthe transparent flattening layer 80 formed is not dissolved into thesolvent in the color filter material.

In order to achieve such excellent flatness, it is preferable that thematerial for the transparent flattening layer use an organic solventhaving high volatility such as alcohol group or cellosolve group withhigh volatility, as does the color filter material. Ethyl cellosolveacetate is actually adopted in the above embodiment. The material whichis hardened with heat treatment and of either non-photosensitive type ornegative type is required.

Non-photosensitive thermosetting material which proceeds with hardeningreaction in all of the constitutional components provides a high degreeof film hardness. An example of this material is polyglycidylmethacrylate. Polyglycidyl methacrylate is positively sensitive to someextent in the side of short wavelength but not in the wavelengths ofG-rays, I-rays, or short wavelength ultraviolet-rays (Deep-UV), makingpatterning impossible in those sides of wavelength. Heat treatment at atemperature of 150° C. or more increases layer hardness due to heatcross-link and also enhances resistance to an organic solvent. Theachieved layer hardness is harder than pencil hardness H.

The negative photosensitive thermosetting material makes cross-link withlight exposure, lowering its solubility to the solvents. The result isincreases in its layer hardness and its resistance to organic solvents.Examples of this material are material including polyglycidylmethacrylate and 4" methacryloylo oxy chalone in its fundamentalstructure.

This material proceeds with thermosetting reaction of polyglycidylmethacrylate in response to heat treatment and the material in chalconegroup, when exposed to short wavelength ultraviolet rays, exhibitsdimerization due to double coupling in benzylic acetophenone group inthe 4" methoxy oxy chalone chain.

4" methacryloylo oxy chalone is absorbed in shorter wave-length sidethan I-rays but is not absorbed in the visible light range, likepolyglycidyl methacrylateas. If sufficient resistance to organicsolvents is not provided by heat treatment alone in the steps of thedrawings, layer hardness is enhanced by light exposure to improve theresistance to organic solvents. The achieved layer hardness is harderthan pencil hardness H, as the non-photosensitive thermosetting materialdoes. A mixed layer may be prevented from developing by the choice ofmaterial and steps as shown above.

Thereafter, as shown in FIG. 24, the color filter base layer 81 isformed on the transparent flattening layer by means of rotaryapplication. Heat treatment is then carried out for a few minutes at atemperature of 70° through 100° C. to evaporate a solvent.

Then, as shown in FIG. 25, the color filter base layer 81 is exposed toI-rays via a desired patterning mask as a photo mask.

The next step of FIG. 26 is to dissolve the unexposed areas of the colorfilter base layer 81 into a developer in alcohol group such as isopropylalcohol or ethanol. After the dissolution, the developer is removed andheat treatment is followed for a few minutes at a temperature ofapproximately 150° C. The color filter pattern 82 is developed throughthese steps.

The next step of FIG. 27 is to dip the finished color filter pattern 82in dyestuffs and wash and dry the same. Dyeing takes place to form thecolor filters by coupling of dyeing radicals included in the colorfilter pattern 82 and dyestuffs. Furthermore, if fixing treatment iscarried out on the color filters, the color filters will never be dyedagain when being soaked in the next dyestuff and will stay unchanged. Asan example, this fixing treatment is achieved by dipping the colorfilters in an aqueous tannin acid solution and then an aqueous antimonypotassium tartrate solution.

As is obvious from FIG. 28, the steps of FIGS. 24 through 26 arerepeated so as to form the second and third color filters 83.

The step of FIG. 29 is to form a transparent flattening layer 84 on thecolor filters 83, subsequently to the formation of all of the colorfilters 83. Micro lenses 85 are formed in order to improve thesensitivity of the solid state imaging device. The transparentflattening layer 84 mounted on the color filters 83 does not needsensitivity, unlike the underlying transparent flattening layer 80.

The final step of FIG. 30 is to remove the transparent flattening layers80 and 84 and the gap filler layer 74 on the bonding pad 73 as theexternal line connection and on the scribe lines 74. The transparentflattening layers 80 and 84 and the gap filler layers 78 are removed bymeans of dry etching method such as O₂ ashing with oxygen plasma.

The gaps on the surface of the light-shielding metal layers 77, thelight-receiving sections 72, and the scribe line 74 in the solid stateimaging element manufactured are finely flattened through the abovesteps

By rotating application of the synthetic photosensitive materials usingthe organic solvent of excellent uniformity on the surface of the finelyflatted transparent flattening layer 80, the color filters 83 are madefree of unevenness. Furthermore, the removing of the gap filler layer 78between the scribe line 14 and the bonding pads 73, and the transparentflattening layers 80 and 84 at the final step of the manufacturingprocess, prevents uneven application during rotary application on colorfilters and thinning of the color filter layer 83 in the areas where thegaps are closed each other. Consequently, the color filters formed fromthe above-mentioned color filter base layers 81 of evenness showexcellent uniformity in shape or topography.

The conventional material of natural protein such as gelatin or caseinand dichromate as a photo sensitizer, experienced a considerabletimewise change due to dark reaction during the manufacturing of thecolor filters. Even if the steps of application, exposure, development,and dyeing were controlled in terms of minutes, it was difficult to forma color filter 83 uniformly on a solid state imaging device.

The diazo compounds used for the synthetic photosensitive materialaccordance with the present invention show an extremely slow timewisechange in organic solvents and hardly change during the manufacturing ofthe color filters. Accordingly, each of the color filters (monocolor)formed in the imaging device is excellent in uniformity of shape. Dyingperformance is subject to no or less variation due to the differentmaterials.

For the reasons described above, the color filters in a single colorcarried on the solid state imaging device exhibit excellent uniformityin shape and photo spectrography. Therefore, the solid state imagingdevice is excellent in shading characteristics, free from irregularityin shape or variation of photo spectrography.

The non-photosensitive thermosetting material or negative photosensitivematerial used for the transparent flattening layer 80 prevents formationof a mixed layer. Therefore, no inferior image with mixed colors causedby a colored mixed-layer is observed.

The synthetic photosensitive materials having solubility to organicsolvents, as used in the embodiments of the present invention, show thecharacteristics of light cross-link. The diazo compounds and azidecompounds are known as a light cross-link sensitizer having ofsolubility to organic solvents. The diazo compounds are different insensitive wavelength range, heat stability, and choices of cross-linkingpolymers, according to the structure thereof. The compounds may be madewater-soluble or soluble to organic solvents according to choice of thekind of counter anion. The azide compounds are likewise different insensitive wavelength range, heat stability, and choices ofbridge-formable polymers, according to the structure thereof. Inaddition, it shows the highest cross-link characteristics tonon-water-soluble polymers. Of all of the above materials, the azidecompounds show high cross-linking efficiency toward the syntheticorganic solvent-soluble polymers compounded for the color filtermaterials and provide high resolution. They show superior resolution, ascompared to the conventional color filter materials of the naturalprotein compounded with dichromate.

Furthermore, the above illustrated embodiments of the present inventionemploys the so-called fixing method, by which to fix the color filter 83after being formed. Other methods to form color filters 83 involve aprotecting layer method by which dye-preventing layers are formed everytime after forming color filters 83 and a window method by which thecolor filter pattern 82 is formed uniformly on the transparentflattening layer 80 and a transparent film is formed thereon to protectfrom color mixing with a window opened for dying only desired areas ofthe color filter patterns 82.

FIG. 31 shows a manufactured method of a solid state imaging device inaccordance with a fifth embodiment of the present invention. The samemethod as for the color filters 83R, 83G, and 83B of red, green and blueis applied to form stripe patterns or light-shield filter 86 to rid theimage characteristics of smear or flare or the like. In this case, thestripe patterns 86 of excellent shape are formed, as compared with theconventional stripe patterns 86 of the natural protein combined withdichromate. It is not possible that the stripe patterns 86 may cover thelight-receiving sections 72, so that the solid state imaging deviceexhibits higher sensitivity.

FIG. 32 shows a manufacturing method of a solid state imaging device inaccordance with a sixth embodiment of the present invention. Thisembodiment uses color filters 83MG, 83CY, 83GR and 83YE of magenta,cyan, green, and yellow in place of the three primary colors of red,green and blue in the previous embodiments. In this case, green color isgenerated by combining yellow and cyan. This method provides the colorfilters 23 of uniformity both in shape and photo spectrography. Thepresent invention provides the solid state imaging device with excellentcharacteristics in sensitivity, free of shading, flickers, color-mixingand so forth.

The present invention has been described in detail for a clearunderstanding, with reference to the embodiments thereof and thedrawings. It is obvious that some changes or modification are possibletherein within the scope of the appended claims.

As is understood from the above description, the present inventionprovides the color filters on the surface of the finely flattenedtransparent layer mounted on the solid state imaging device, using thesynthetic photosensitive materials with excellent uniformity of itsapplication and stability on time. Each of the color filters in a singlecolor on the solid state imaging device using the syntheticphotosensitive material is excellent in shape and photo spectrography,while meeting the demand of downsizing and a higher number of pixies inthe solid state imaging device. The solid state imaging device providesprominent image characteristics which are free of color mixing orinferiority in flickers or shading caused by non-uniform shape ordifference of photo spectrography in the color filters and also imageinferiority due to particles or white blemish.

Therefore, the spirit and scope of the appended claims should not belimited to the description of the preferred versions contained herein.

What is claimed is:
 1. A solid state imaging device comprising:asemiconductor substrate having a light-receiving section; a transparentflattening layer on the semiconductor substrate; and a color filter ofsynthetic photosensitive material, formed on the transparent flatteninglayer by using water as a solvent.
 2. A solid state imaging devicecomprising:a semiconductor substrate having a first light-receivingsection and a second light-receiving section formed adjacent each other;a transparent flattening layer on the semiconductor substrate; and ablack stripe, formed on the transparent flattening layer between thefirst and second light-receiving sections by using water as a solvent.3. A solid state imaging device according to claim 1 or 2 wherein thetransparent flattening layer includes positive type photosensitivethermosetting material.
 4. As solid state imaging device according toclaim 3 wherein the positive type photosensitive thermosetting materialincludes polymethyl methacrylate and polyglycidyl methacrylate.
 5. Asolid state image device comprising:a semiconductor substrate having alight-receiving section; a transparent flattening layer ofnon-photosensitive thermosetting material or negative typephotosensitive thermosetting material, on the semiconductor substrate,and a color filter of synthetic photosensitive material formed of thetransparent flattening layer.
 6. A solid state imaging devicecomprising:a semiconductor substrate having first and secondlight-receiving sections; a transparent flattening layer ofnon-photosensitive thermosetting material or negative typephotosensitive thermosetting material, on the semiconductor substrate;and a black stripe of synthetic photosensitive material formed on thetransparent flattening layer between the first and secondlight-receiving sections.
 7. A solid state imaging device according toclaim 5 or 6 wherein the color filter or the black stripe is formed ofsynthetic photosensitive material which contains an organic solvent as asolvent.
 8. A solid state imaging device according to claim 5 or 6wherein the color filter or the black stripe is formed of syntheticphotosensitive material containing an azide compound of photobridgingtype as sensitizer and an organic solvent as a solvent.
 9. A solid stateimaging device according to claim 1, 2, 5 or 6 wherein the syntheticphotosensitive material for the color filter or black stripe contains inwater an acrylic copolymer, oxy poly basic acid salt and a diazocompound of light cross-link type.
 10. A solid state imaging deviceaccording to claim 9 wherein said acrylic compound contained in thesynthetic photosensitive material for the color filter or black stripeis represented by the following general expression in the range of 5,000through 100,000 of average molecule weight: ##STR2## wherein R₁represents a hydrogen atom or CH₃, R₂ and R₃ represent an alkyl group orallyl group such as CH₃, C₂ H₅, C₆ H₅ and the like independently, and nrepresents an integer from 1 to 10; and said acrylic compound comprises5-20 weight % of a monomer, 45-55 weight % of 2-hydroxy ethylmethacrylate; 20-30 weight % of methacrylic amide; and 5-10 weight % ofbenzylic methacrylate.
 11. A solid state imaging device according toclaim 9 wherein the diazo compound contained in the syntheticphotosensitive material for the color filter or the black stripecomprises a polycondensation product including diphenylamine-4-diazoniumsalt or its derivative and formaldehyde.
 12. A solid state imagingdevice according to claim 11 wherein the diphenylamine-4-diazonium saltor its derivative includes at least one of diphenylamine-4-diazoniumsalt 3-methoxyl diphenylamine-4 diazonium chloride.
 13. A solid stateimaging device according to claim 9 wherein the diazo compound containedin the synthetic photosensitive material for the color filter or theblack stripe comprises a polycondensation product includingdiphenylamine-4-diazonium salt or its derivative, and4,4'-bis-methoxylmethyl diphenylether.
 14. A solid state imaging deviceaccording to claim 13 wherein the diphenylamine-4-diazonium salt or itsderivative includes at least one of diphenylamine-4-diazonium salt and3-methoxyl diphenylamine-4 diazoium chloride.
 15. A solid state imagingdevice according to claim 9 wherein the diazo compound contained in thesynthetic photosensitive material for the color filter or the blackstripe comprises a compound not including an amino radical.
 16. A solidstate imaging device according to claim 15 wherein the diazo compoundcontained in the synthetic photosensitive material for the color filteror the black stripe includes one or more couplings out of--C(CH₂)q-- (qis an integer from 1 to 5) or --O--R₆ --O-- (R₆ is 6 through 12C--carbonatoms or aryl) or --O-- or --S--in the diphenylamine-4-diazonium salt orphenyl radicals in its derivative.
 17. A method of manufacturing a solidstate imaging device comprising the steps of:forming a transparentflattening layer on a semiconductor substrate to cover a scribe line anda bonding pad, using positive photosensitive thermosetting material; andforming a color filter or a black stripe on a surface of the transparentflattening layer by means of exposure and development, usingphotosensitive material containing water as a solvent; and removing thetransparent flattening layer on the scribe line and the bonding pad bymeans of exposure and development.
 18. A method of manufacturing a solidstate imaging device according to claim 17, wherein the step of formingthe color filter or black stripe on of the transparent flattening layerby means of exposure and development, forms the color filter or blackstripe by means of coloring with desired dyestuffs after a color filterpattern or black stripe pattern is formed.
 19. A method of manufacturinga solid state imaging device comprising the steps of:forming atransparent flattening layer on a semiconductor substrate to cover ascribe line and a bonding pad, using non-photosensitive thermosettingmaterial; treating the transparent flattening layer with heat to form acolor filter or a black stripe on the transparent flattening layerusing, synthetic photosensitive material; and removing the transparentflattening layer on the scribe line and bonding pad by means of dryetching.
 20. A method for manufacturing a solid state imaging devicecomprising the steps of:forming a transparent flattening layer on asemiconductor substrate to cover a scribe line and a bonding pad, usingnegative thermosetting material; treating the transparent flatteninglayer with heat or light exposure or both; forming a color filter orblack stripe on the transparent flattening layer, using syntheticphotosensitive material containing an organic solvent; and removing thetransparent flattening layer on the scribe line and the bonding pad bymeans of dry etching.
 21. A solid state imaging device comprising:asemiconductor substrate having a light-receiving section; a plurality ofdiscrete color filters of red, green and blue colors, formed over thelight-receiving section of the semiconductor substrate at intervals,each color filter made of synthetic photosensitive material; and aplurality of black stripes formed over the light-receiving section ofthe semiconductor substrate to lie between the adjacent discrete colorfilters, each black stripe made of synthetic photosensitive material.